Rt-PCR study of purinergic P2 receptors in hematopoietic cell lines

Seven P2X and fifteen P2Y receptors have been identified to date, partly on the basis of amino acid sequence homologies. The expression of all cloned human purinergic P2 receptors was investigated on the messenger RNA level in promonocytic U937 cells, erythroblastic K562 cells, and undifferentiated, dimethyl sulfoxide-differentiated granulocytic, and phorbol-12-myristate-13-acetate-differentiated monocytic HL60 cells. RT-PCR assays showed expression of several P2X receptors, whereas all P2Y receptors were found in at least some of the analyzed cells lines. Granulocytic and monocytic differentiation of HL60 cells lead to a partly dramatic up- or downregulation of receptor transcripts. The number of different P2 receptors expressed in each cell type showed a significant rise from U937 cells via K562 cells, undifferentiated and granulocytic, to monocytic HL60 cells. The total mRNA amounts being normalized to the glyceraldehyde-3-phosphate dehydrogenase levels demonstrated an even more distinct variability of absolute transcript levels. An increased number of different P2 receptors expressed were associated with an increased total average P2 receptor mRNA amount in each cell. This phenomenon of overexpression suggests self-inductive effects of purinergic signaling indicating its involvement in hematopoiesis and possibly in immunoreactive mediation.